The present invention relates to a method for managing communication resources between nodes of a network, and more particularly to a dynamic distributed multi-channel Time Division Multiple Access (TDMA) slot assignment method that uses channelized neighborhoods.
Mobile multi-hop broadcast packet radio networks are known for their rapid and convenient deployment, self organization, mobility, and survivability. In this type of network as illustrated in FIG. 1, a transmission from one node, for example node 1, is broadcast to all nodes in its xe2x80x9cneighborhoodxe2x80x9d. Ultra-high frequency (UHF) systems generally have a neighborhood defined by nodes within line of sight of the transmitting node (these nodes being termed within one xe2x80x9chopxe2x80x9d of the transmitting node). For example, in FIG. 1 nodes 1, 3, 4, 5, 6, 7, and 8 make up one neighborhood. For data transmitted from node 1 to propagate multiple hops, the data must be relayed by one or more of node 1""s neighbors. For example, node xe2x80x9caxe2x80x9d (likewise nodes b, c, and g) is two hops away from the node 1 transmitter. The data will be relayed in this manner until it has arrived at all intended destination nodes.
Since there are generally limitations on the number of simultaneous transmissions that a receiver can successfully process (typically one), collisions can be avoided by the assignment of time slots in which individual nodes can transmit. There are many approaches to deciding which nodes are assigned which slots, and the approach is generally driven by the network applications, such as, broadcast, multicast, unicast, datagrams, virtual circuits, etc. Because the problem of optimally assigning slots in this environment is mathematically intractable, a heuristic approach is taken to design an integrated protocol that both chooses the number of slots to assign to each neighboring node and coordinates their activation in the network.
Tactical military and commercial applications require self-organizing, wireless networks that can operate in dynamic environments and provide peer-to-peer, multi-hop, multi-media communications. Key to this technology is the ability of neighboring nodes to transmit without interference. Neighboring nodes transmit without interference by choosing time slots and channels that do not cause collisions at the intended unicast or multicast receivers. This functionality is provided by the Unifying Slot Assignment Protocol (USAP) which is the subject of U.S. Pat. No. 5,719,868 the disclosure of which is herein incorporated by reference. The function of USAP is to monitor the RF environment and allocate the channel resources on demand and automatically detect and resolve contention resulting from changes in connectivity.
Wireless channel access schemes traditionally come in two flavors: contention and reservation. Contention has been the favorite for ad hoc broadcast networks because its lack of structure lends itself well to the mobile environment. Also, low access delays make it suitable for both tactical voice, where push-to-talk is the norm, and bursty data. However, when the network is heavily loaded contention is inefficient. At that point a structured access like reservation Time Division Multiple Access (TDMA) can achieve much higher efficiencies.
Another division in this field is the difference between broadcast and unicast. Broadcast techniques, in which a node transmits to all of its neighbors, and unicast techniques, in which a node transmits to only one of its neighbors, both have their own unique advantages dependent upon the application. Traditional wireless systems, however, are not capable of utilizing both broadcast and unicast schemes.
Ideally, a wireless channel access system would support both reserved circuits and datagrams in whatever combination is required. Conventional wireless channel access systems however are not capable of supporting both reserved circuits and datagrams.
Conventional wireless communication systems are capable of handling only one or a small number of data types, including low latency voice, delay tolerant data, bursty transactions, high throughput streams, error sensitive data, and error tolerant video. However, conventional systems are not capable of handling the full range of data types.
Conventional wireless communications systems are typically capable of establishing and maintaining only one type of virtual circuit, including either the establishment and maintenance of hard circuits or the establishment and maintenance of permanent datagram service.
Thus, there is a need and desire for a channel access scheme to use TDMA for wireless communication capable of using both broadcast and unicast techniques dependent upon the state of the communication environments. Further still, there is a need and desire for a wireless communication system that is able to handle a full range of data types including low latency voice, delay tolerant data, bursty transactions, high throughput streams, error sensitive data, and error tolerant video. Further still, there is a need and desire for a channel access system that is capable of providing both reserve circuits and datagram service. Further still, there is a need and desire for a wireless communication system that is able to handle the full range of data types while optimizing for densities ranging from fully connected to sparse and, because of its reliance only on local information, scaling to large network sizes.
The present invention relates to a method for automatically managing communication channel resources between nodes having neighboring nodes in a network of nodes. Each node communicates during specific time slots on a time multiplex basis. The method includes communicating between nodes in the network using a time division multiple access structure that include broadcast cycles having a plurality of time frames. Each time frame includes a plurality of time slots and a plurality of frequency channels. The method further includes storing, at each node an assignment of possible time slots and frequency channels to communicate between nodes in the network, and grouping neighboring nodes of a particular nodes into at least first and second groups when the number of neighboring nodes of a particular node exceeds a predetermined limit. The method also includes assigning a first frequency channel to the first group on which to transmit communications to other nodes, and assigning a second frequency channel to the second group on which to transmit communications to other nodes. The present invention further relates to a communication system having a plurality of transceiver nodes with neighboring nodes in a network of nodes. The nodes are configured to communicate on the network using a time division multiple access structure which includes time frames, each time frame having time slots and frequency channels. An assignment of possible time slots and frequency channels in and on which to communicate to other nodes is stored at each node. The system also includes a channelized neighborhooding protocol to group neighboring nodes of a particular transceiver node into at least first and second groups, and to assign a schedule of possible frequency channels to the first and second groups for transmitting communications during one or more time frames.
The present invention still further relates to a method for automatically managing the communication channel resources between nodes having neighboring nodes in a network of nodes. Each node communicates during specific time slots and uses multiple channels on a time multiplex basis. The method includes communicating between nodes in the network using a time division multiple access structure which includes times slots and frequency channels arranged within each of a plurality of frames of a time division. The method further includes storing, at each node, a table of possible time slots and frequency channels to communicate between nodes during each time frame. The method also includes grouping the neighboring nodes of a particular node into first and second groups, and grouping a portion of the nodes in the first group and a portion of the nodes in the second group as members of a third group. The method further includes scheduling the members of the third group to listen on particular frequency channels, respectively, and rescheduling the members of the third group to listen on different frequency channels, respectively.